<!DOCTYPE html>
<html>
<head>
	<script src="test.js">		
	</script>
</head>
<body>	
	<div id="message">[message]</div>
	</br>
	<button onclick="toggleVisibility('message');">Hide / Unhide</button>
	<br/>
	<a href="#" onclick="toggleVisibility('foo');">Click here to toggle visibility of element #foo</a>
	<div id="foo">I am foo.</div>	
</body>
</html>